45 1. In risk, what are the main difference(s) between the toxicity quotient app

Question

45

1. In risk, what are the main difference(s) between the toxicity quotient approach and the hazardous quotient approach?

2. Why can sediments become important in a risk assessment?

3. What processes may retard chemical movement in the environment?

4. What is the difference between porosity and permeability?

5. If incineration can be effective for destroying contaminants, why isn’t it used more often? What other similar technique could be used in its place and explain why?

6. What kind of treatment technology is often used with carbon adsorption to remove contamination from groundwater?

7. When there is VOC contamination in the groundwater, what technology would be useful to use with air sparging.

8. When can thermal enhancement of technologies be effective?

Explanation / Answer

4) The porosity of a soil refers to the volume of all the open spaces (pores) between the solid grains of soil. For growing things in soil, the porosity is important as it defines the volume of water that can be held in a given volume of the soil.

Soil permeability is the property of the soil pore system that allows fluid to flow. It is generally the pore sizes and their connectivity—how well those pore spaces allow water to flow through the soil—that determines whether a soil has high or low permeability. Water will flow easily through soil with large pores with good connectivity between them. Small pores with the same degree of connectivity would have lower permeability, because water would flow through the soil more slowly. It is possible to have zero permeability (no flow) in a high porosity soil if the pores not connected. Near zero permeability also occurs if the pores are very small, such as in clay.

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